Multi-plug launching system and method

ABSTRACT

In accordance with one aspect of the disclosure, a system includes a multiple cement plug launching system having a plug system adapter assembly, a first plug assembly comprising a first central passage and a plurality of rupture disks, wherein each rupture disk of the plurality of rupture disks occludes a respective one of a plurality of rupture disk ports extending through the first plug assembly, and a second plug assembly comprising a second central passage, wherein the plug system adapter assembly is coupled to the second plug assembly, which is coupled to the first plug assembly, such that the plug system adapter assembly, the second plug assembly, and the first plug assembly are coupled to one another in an axial arrangement.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 62/329,898, entitled “MULTI-PLUG LAUNCHING SYSTEM AND METHOD,” filed Apr. 29, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND

Embodiments of the present disclosure relate generally to the field of drilling and processing of wells. More particularly, present embodiments relate to a system and method for launching multiple cement plugs during casing operations.

Cement plugs are typically utilized during casing operations to substantially remove cement or other fluid from an interior surface of wellbore tubulars. In conventional oil and gas operations, an annulus is formed around the wellbore tubulars within a formation. During completion operations, casing (e.g., wellbore tubulars) may be secured to the formation via cementing. The cement is pumped through the casing to fill the annulus and secure the casing to the formation. After cement pumping is complete, a cement plug is introduced into the casing to clear the cement from the interior surface of the casing. As a result, cementing operations may continue with little to no mixing of cement with the drilling/displacement fluids pumped through the casing. In certain embodiments, multiple cement plugs may be used if different types of fluids (e.g., drilling mud, cement slurries of varying consistency or density, displacement fluids, etc.) are used during the casing operations. Unfortunately, traditional multi-plug systems are large and/or long, which presents complications when used with smaller derricks or drilling rigs.

BRIEF DESCRIPTION

In accordance with one aspect of the disclosure a multiple cement plug launching system includes a plug system adapter assembly, a first plug assembly comprising a first central passage, a second plug assembly comprising a second central passage, a first plurality of shear screws coupling the first plug assembly to the second plug assembly, and a second plurality of shear screws coupling the second plug assembly to the plug system adapter.

In accordance with another aspect of the disclosure, a method includes inserting a multiple cement plug launching system with a casing string, wherein the multiple cement plug launching system comprises a first plug assembly, a second plug assembly coupled to the first plug assembly, and a plug system adapter assembly coupled to the second plug assembly, launching the first plug assembly down the casing string, rupturing a plurality of rupture disks of the first plug assembly after launching the first plug assembly down the casing string; and launching the second plug assembly down the casing string after rupturing the plurality of rupture disks in the first plug assembly.

In accordance with another aspect of the disclosure, a system includes a multiple cement plug launching system having a plug system adapter assembly, a first plug assembly comprising a first central passage and a plurality of rupture disks, wherein each rupture disk of the plurality of rupture disks occludes a respective one of a plurality of rupture disk ports extending through the first plug assembly, and a second plug assembly comprising a second central passage, wherein the plug system adapter assembly is coupled to the second plug assembly, which is coupled to the first plug assembly, such that the plug system adapter assembly, the second plug assembly, and the first plug assembly are coupled to one another in an axial arrangement.

DRAWINGS

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic of a drilling rig, illustrating a multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 2 is a partial cross-sectional side view of an embodiment of a multi-plug launching system coupled to a tubular gripping system, in accordance with an embodiment of the present techniques;

FIG. 3 is a cross-sectional side view of an embodiment of a multi-plug launching system disposed within a tubular, in accordance with an embodiment of the present techniques;

FIG. 4 is a cross-sectional side view, taken within line 4-4 of FIG. 3, illustrating a coupling between a top plug assembly and a bottom plug assembly of the multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 5 is a side view of a top plug assembly of a multi-plug launching system, in accordance with an embodiment of present techniques;

FIG. 6 is a cross-sectional side view, taken along line 6-6 of FIG. 5, of the top plug assembly of a multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 7 is a side view of a bottom plug assembly of a multi-plug launching system, in accordance with an embodiment of present techniques;

FIG. 8 is a cross-sectional side view, taken along line 8-8 of FIG. 7, of the bottom plug assembly of a multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 9 is a cross-sectional side view of another embodiment of the bottom plug assembly of a multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 10 is a cross-sectional side view of the multi-plug launching system disposed within a tubular string, illustrating operation of the multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 11 is a cross-sectional side view of the multi-plug launching system disposed within a tubular string, illustrating operation of the multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 12 is a cross-sectional side view of the multi-plug launching system disposed within a tubular string, illustrating operation of the multi-plug launching system, in accordance with an embodiment of the present techniques;

FIG. 13 is a cross-sectional side view of a bottom plug assembly of the multi-plug launching system disposed within a tubular string, illustrating the bottom plug assembly launched to the bottom of the tubular string, in accordance with an embodiment of the present techniques;

FIG. 14 is a cross-sectional side view of the multi-plug launching system disposed within a tubular string, illustrating operation of the multi-plug launching system, in accordance with an embodiment of the present techniques; and

FIG. 15 is a cross-sectional side view of the multi-plug launching system disposed within a tubular string, illustrating operation of the multi-plug launching system, in accordance with an embodiment of the present techniques.

DETAILED DESCRIPTION

Present embodiments provide a system and method for launching multiple cement plugs within a casing or other tubular. For example, during casing cementing operations, one or more plugs (e.g., cement plugs) are used to substantially remove drilling mud from an interior surface of wellbore tubulars (e.g., casing) prior to a cementing process. Similarly, one or more plugs may be used to separate cement from displacement fluid and/or separate cement from drilling mud as the plug is launched to substantially remove cement from the interior surface of wellbore tubulars (e.g., casing). Additionally, in certain embodiments, multiple cement plugs may be used in systems where cements of different density or constituency are used to seal and set different sections of a well. Present embodiments include a multi-plug launching system having a first plug (e.g., a bottom plug) and a second plug (e.g., a top plug) that are coupled to one another. However, additional numbers of plugs may be used in accordance with the present techniques. The second plug (e.g., the top plug) is also coupled to an adapter assembly to enable coupling of the first plug and the second plug to a tubular gripping system (e.g., a casing running tool). With the first and second plugs coupled to the tubular gripping system, the multi-plug launching system may be inserted into (e.g., “stabbed” into) a tubular string (e.g., casing). The first and second plugs each include a port to allow a fluid (e.g., spacer fluid, cement, etc.) to pass through the plugs and into the casing or tubular.

After a casing running operation is completed, the casing string within the wellbore may be filled with drilling mud. Prior to beginning a casing cementing process, a first solid ball (e.g., small solid ball) is launched to occlude the port of the bottom plug. Thereafter, a cement slurry and/or a spacer fluid is pumped through the second plug (e.g., top plug) and behind the first solid ball and bottom plug, thereby creating pressure and causing shear screws coupling the bottom plug to the top plug to shear and launch the bottom plug down the casing string. After the bottom plug is launched, cement is pumped through the top plug and behind the bottom plug to drive the bottom plug down the casing or tubular string until the bottom plug reaches the bottom of the casing or tubular string. As discussed below, the bottom plug may include rupture disks that occlude additional ports of the bottom plug. The cement may be pumped through the top plug and into the casing until the rupture disks of the bottom plug at the bottom of the casing shatter and open the additional ports. With the additional ports of the bottom plug opened, the cement may flow out of the casing string and into an annulus between the casing string and the wellbore.

Once a desired or calculated amount of the cement is pumped through the top plug into the casing (e.g., to rupture the rupture disks of the bottom plug at the bottom of the casing and/or fill the annulus between the casing string and the wellbore), a second solid ball (e.g., large solid ball) may be launched to occlude the port of the top plug. Thereafter, a displacement fluid (e.g., water or a water mixture) is pumped behind the second solid ball and the top plug, thereby creating pressure and causing shear screws coupling the top plug to the adapter assembly to shear and launch the top plug down the casing or tubular string. Thereafter, the displacement fluid may be locked in the casing string until the previously-pumped cement is cured. Present embodiments of the multi-plug launching system are shorter than traditional multi-plug launching systems. Thus, as the disclosed systems are inserted into the casing, they may take up little or no stack-up room on the derrick or rig.

Turning now to the drawings, FIG. 1 is a schematic view of a drilling rig 10 in the process of drilling a well in accordance with present techniques. The drilling rig 10 features an elevated rig floor 12 and a derrick 14 extending above the rig floor 12. A supply reel 16 supplies drilling line 18 to a crown block 20 and traveling block 22 configured to hoist various types of drilling equipment above the rig floor 12. The drilling line 18 is secured to a deadline tiedown anchor 24, and a drawworks 26 regulates the amount of drilling line 18 in use and, consequently, the height of the traveling block 22 at a given moment. Below the rig floor 12, a casing string 28 extends downward into a wellbore 30 and is held stationary with respect to the rig floor 12 by a rotary table 32 and slips 34 (e.g., power slips). A portion of the casing string 28 extends above the rig floor 12, forming a stump 36 to which another length of tubular 38 (e.g., a section of casing) may be added.

A tubular drive system 40, hoisted by the traveling block 22, positions the tubular 38 above the wellbore 30. In the illustrated embodiment, the tubular drive system 40 includes a top drive 42 and a gripping device 44 (e.g., a casing drive system or casing running tool). The gripping device 44 of the tubular drive system 40 is engaged with a distal end 48 (e.g., box end) of the tubular 38. The tubular drive system 40, once coupled with the tubular 38, may then lower the coupled tubular 38 toward the stump 36 and rotate the tubular 38 such that it connects with the stump 36 and becomes part of the casing string 28. The casing string 28 (and the tubular 38 now coupled to the casing string 28) may then be lowered (and rotated) further into the wellbore 30.

The gripping device 44 (e.g., casing drive system or casing running tool) is configured to reciprocate and/or rotate the tubular 38 (e.g., casing) during casing and/or cementing operations. The gripping device 44 may also be used during cementing operations to direct cement into the casing string 28. In certain embodiments, the gripping device 44 may be coupled to a cement swivel configured to supply cement for cementing operations. For example, the cement swivel may receive cement from a pumping unit via a supply line. Additionally, the gripping device 44 may include an inner bore configured to direct the cement through the gripping device 44 and into the casing string 28.

As mentioned above, present embodiments also include a multi-plug launching system 50 (e.g., a multiple cement plug launching system), which is used to launch multiple plugs down the casing string 28 during cementing operations. In the illustrated embodiment, the multi-plug launching system 50 is shown set aside on the drilling rig 10 and is not in use. The embodiments of the multi-plug launching system 50 described herein include a first plug (e.g., a bottom plug or first plug assembly) 52, a second plug (e.g., a top plug or second plug assembly) 54, and a plug system adapter 56 (e.g., a plug system adapter assembly), which are coupled together in an axial arrangement (e.g., the respective central axes of the first plug 52, the second plug 54, and the plug system adapter 56 are generally aligned and/or are coaxial). It will be appreciated that other embodiments of the multi-plug launching system 50 may include additional numbers of plugs (e.g., 3, 4, 5, or more) depending on design considerations, numbers or types of cement used, numbers of casing string 28 sections to be cemented, etc. For example, the first plug 52 of the multi-plug launching system 50 may be launched down the casing string 28 to clean drilling mud from an interior wall of the casing string 28 after the casing string 28 is run into the wellbore 30 and prior to beginning the cementing process. Once the first plug 52 is launched, cement may be pumped through the gripping device 44, the plug system adapter 56, and the second plug 54 and behind the first plug 52 to drive the first plug 52 to the bottom of the casing string 28. As discussed below, cement may be pumped until rupture disks of the first plug 52 are ruptured to enable passage of the cement through the first plug 52 at the bottom of the casing string 28 and into an annulus between the casing string 28 and the wellbore 30. After a desired or calculated amount of cement is pumped into the casing string 28, the second plug 54 of the multi-plug launching system 50 may be launched down the casing string 28 (e.g., using a displacement fluid) to clean or wipe the cement from the interior wall of the casing string 28. As discussed below, the multi-plug launching system 50 has a compact configuration that enables the multi-plug launching system 50 to be inserted into or “stabbed” into the casing string 28 without taking up any or any significant stack-up room on the drilling rig 10.

It should be noted that the illustration of FIG. 1 is intentionally simplified to focus on the multi-plug launching system 50 of the drilling rig 10, which is described in greater detail below. Many other components and tools may be employed during the various periods of formation and preparation of the well. Similarly, as will be appreciated by those skilled in the art, the orientation and environment of the well may vary widely depending upon the location and situation of the formations of interest. For example, rather than a generally vertical bore, the well, in practice, may include one or more deviations, including angled and horizontal runs. Similarly, while shown as a surface (land-based) operation, the well may be formed in water of various depths, in which case the topside equipment may include an anchored or floating platform. Furthermore, it will be appreciated that the disclosed multi-plug launching system 50 may have other components (e.g., additional plugs) and may be used with different fluids (e.g., drilling mud, spacer fluids, cements of different consistencies and/or densities, displacement fluids, etc.) in different orders.

FIG. 2 is a partial cross-sectional side view of the multi-plug launching system 50 coupled to the gripping device 44 (e.g., casing drive system or casing running tool) prior to insertion of the multi-plug launching system 50 into the casing string 28. As mentioned above, the multi-plug launching system 50 includes the first plug (e.g., bottom plug) 52, the second plug (e.g., top plug) 54, and the plug system adapter 56. The first plug 52 is coupled to the second plug 54, and the second plug 54 is coupled to the plug system adapter 56. Details of the connections between these components are described in further detail below. The plug system adapter 56 is coupled to the gripping device 44 to enable insertion or “stabbing” of the multi-plug launching system 50 into the casing string 28. For example, as shown in the illustrated embodiment, the plug system adapter 56 may be threaded to a distal end 60 of a mandrel 62 of the gripping device 44 via a threaded portion 64 of the plug system adapter 56.

FIG. 3 is a cross-sectional side view of the multi-plug launching system 50 inserted or “stabbed” into the casing string 28. The gripping device 44 is not shown. In the illustrated embodiment, the plug system adapter 56 includes a central port 70 extending from an axial top 72 of the plug system adapter 56 to an axial bottom 74 of the plug system adapter 56. The central port 70 enables a flow of fluid (e.g., spacer fluid, cement, displacement fluid, etc.) to flow from the gripping device 44 through the plug system adapter 56 to the second plug 54, which is coupled to the central port 70 at the axial bottom 74 of the plug system adapter 56. The second plug 54 (e.g., the top plug) is coupled to the central port 70 via shear pins or screws (e.g., brass shear screws) 76 to enable launching of the second plug 54 in the manner described below. For example, the second plug 54 may be coupled to the central port 70 with eight shear screws 76 with each shear screw 76 having a known shearing force value.

The plug system adapter 56 also includes packer cups 78 disposed about the central port 70. The packer cups 78 form a sealing interface with an internal surface 80 of the casing string 28 to seal an internal cavity 82 of the casing string 28 from the surrounding atmosphere. The illustrated embodiment of the multi-plug launching system 50 includes two packer cups 78, but other embodiments may include other numbers of packer cups 78 (e.g., 1, 3, 4, or more).

As mentioned above, the first plug 52 (e.g., the bottom plug) is coupled to the second plug 54 (e.g., the top plug). For example, FIG. 4 is a cross-sectional side view, taken within line 4-4 of FIG. 3, illustrating a connection between the first plug 52 and the second plug 54. In particular, the first plug 52 and the second plug 54 are coupled to one another via shear pins or screws 90 (e.g., brass shear screws). For example, six shear screws 90, each having a known shearing value, may be used to couple the first plug 52 to the second plug 54. It should be noted that the number of shear screws 90 coupling the first plug 52 to the second plug 54 may be less than the number of shear screws 76 coupling the second plug 54 to the plug system adapter 56. Additionally or alternatively, the shearing force of the shear screws 76 may be greater than the shearing force of the shear screws 90. It will be appreciated that the shear screws 76 are stronger and/or more numerous to ensure that the first plug 52 is launched before the second plug 54 during the cementing operation.

FIGS. 5 and 6 illustrate details of an embodiment of the second plug 54 (e.g., the top plug). For example, FIG. 5 is a side view of the second plug 54, and FIG. 6 is a cross-sectional side view, taken along line 6-6 of FIG. 5, of the second plug 54, illustrating internal components of the second plug 54. The second plug 54 (e.g., second plug assembly) includes an outer body 100, an inner core 102, and a central insert 104. In certain embodiments, the outer body 100 may be formed from rubber or other elastomeric material, and the inner core 102 may be formed from a metal, such as aluminum, a phenolic material, or other suitable material that may provide rigidity to the second plug 54. The central insert 104 may also be formed from a metal, such as aluminum.

The outer body 100 includes a plurality of fins 106 extending radially outward (e.g., relative to a central axis 107 of the second plug 54) and configured to engage tightly with the internal surface 80 of the casing string 28 when the multi-plug launching system 50 is inserted into the casing string 28. As will be appreciated, the fins 106 enable wiping or cleaning of the internal surface 80 of the casing string 28 (e.g., clearing of mud, cement, or other fluid) as the second plug 54 is launched down the casing string 28. The fins 106 also create a seal or barrier between a fluid below the second plug 54 (e.g., cement) and a fluid above the second plug 54 (e.g., displacement fluid) when the second plug 54 is launched down the casing string 28. The outer body 100 also includes a flared portion 108 at an axial top 110 of the second plug 54. The flared portion 108 defines a cavity 112 (e.g., annular cavity) with the central insert 104, which captures the fluid (e.g., cement, spacer fluid, displacement fluid, etc.) pumped through the multi-plug launching system 50 to launch the second plug 54 and drive it down the casing string 28.

As shown in FIG. 6, the central insert 104 axially captures the outer body 100 via flanges 114 of the central insert 104. Similarly, the outer body 100 axially captures the inner core 102 via flanges 116 of the outer body 100. The central insert 104 defines a central passage 118 through which a fluid, such as cement, spacer fluid, or displacement fluid, may flow (e.g., from the plug system adapter 56 to the first plug 52). The central insert 104 also includes a tapered throat portion 120, which partially defines the central passage 118. For example, the tapered throat portion 120 may have a taper of approximately 0.5, 1, 2, 3, or 4 degrees from a first end 122 of the tapered throat portion 120 to a second end 124 of the tapered throat portion 120. The tapered throat portion 120 is designed to capture a first (e.g., large) solid ball launched through the plug system adapter 56 to occlude the central passage 118. Thus, a smallest diameter 126 of the tapered throat portion 120 may be slightly smaller than a diameter of the central port 70 of the plug system adapter 56 to allow the first (e.g., large solid ball to travel through the plug system adapter 56, but not through the tapered throat portion 120 of the second plug 54.

The central insert 104 also includes an adapter portion 128 at an axial bottom 130 of the second plug 54. The adapter portion 128 is configured to couple with (e.g., receive) the first plug 52. To this end, the adapter portion 128 includes holes 132 (e.g., threaded holes) configured to accept or receive the shear screws 90 used to couple the second plug 54 to the first plug 52. Similarly, an axial top 134 of the central insert 104 includes a groove (e.g., annular groove) 136 configured to capture or engage with the screws 76 used to couple the second plug 54 to the plug system adapter 56.

FIGS. 7-9 illustrate details of embodiments of the first plug 52 (e.g., the bottom plug). For example, FIG. 7 is a side view of the first plug 52, and FIG. 8 is a cross-sectional side view, taken along line 8-8 of FIG. 7, of the first plug 52, illustrating internal components of the first plug 52. FIG. 9 is a cross-sectional side view of an alternative embodiment of the first plug 52. The first plug 52 includes similar elements as the second plug 54. For example, the first plug 52 (e.g., first plug assembly) includes an outer body 200, an inner core 202, and a central insert 204. In certain embodiments, the outer body 200 may be formed from rubber or other elastomeric material, and the inner core 202 may be formed from a metal, such as aluminum, a phenolic material, or other suitable material that may provide rigidity to the first plug 52. The central insert 204 may also be formed from a metal, such as aluminum.

The outer body 200 includes a plurality of fins 206 extending radially outward (e.g., relative to a central axis 207 of the first plug 52) and are configured to engage tightly with the internal surface 80 of the casing string 28 when the multi-plug launching system 50 is inserted into the casing string 28. As will be appreciated, the fins 206 enable wiping or cleaning of the internal surface 80 of the casing string 28 (e.g., clearing of mud, cement, or other fluid) as the first plug 52 is launched down the casing string 28.

The fins 206 also create a seal or barrier between a fluid below the first plug 52 (e.g., drilling mud) and a fluid above the first plug 52 (e.g., cement) when the first plug 52 is launched down the casing string 28. The outer body 200 also includes a flared portion 208 at an axial top 210 of the first plug 52. The flared portion 208 defines a cavity 212 (e.g., annular cavity) with the central insert 204 which captures the fluid (e.g., cement, spacer fluid, displacement fluid, etc.) pumped through the multi-plug launching system 50 to launch the first plug 52 and drive it down the casing string 28.

As shown in FIG. 8, the central insert 204 is coupled to the outer body 200 and the inner core 202 (e.g., via molding). The central insert 204 defines a central passage 214 through which a fluid, such as cement, spacer fluid, or displacement fluid, may flow (e.g., from the second plug 54). The central insert 204 also includes a tapered throat portion 216, which partially defines the central passage 214. For example, the tapered throat portion 216 may have a taper of approximately 0.5, 1, 2, 3, or 4 degrees from a first end 218 of the tapered throat portion 216 to a second end 220 of the tapered throat portion 216. The tapered throat portion 216 is designed to capture a second (e.g., small) solid ball launched through the plug system adapter 56 and the second plug 54 to occlude the central passage 214. Thus, a smallest diameter 222 of the tapered throat portion 216 may be slightly smaller than the smallest diameter 126 of the central insert 104 of the second plug 54 to allow the second (e.g., small) solid ball to travel through the plug system adapter 56 and the second plug 54 without disturbing the second plug 54. However, the second (e.g., small) solid ball is sized such that the tapered throat portion 216 captures the second (e.g., small) solid ball to enable launching of the first plug 52 from the second plug 54. The central insert 204 also includes a groove 246 (e.g., annular groove) formed at an axial top 248 of the central insert 204. The groove 246 is configured to receive and engage with the shear screws 90 used to couple the first plug 52 to the second plug 54 when the axial top 248 of the central insert 204 is disposed within the adapter portion 128 of the second plug 54

As shown in FIG. 8, the first plug 52 also includes rupture disks 250 (e.g., axial rupture disks), which are circumferentially arrayed about the central insert 204. The rupture disks 250 are secured to the outer body 200, and each rupture disk 250 occludes a respective rupture disk port 252, which extends through the outer body 200 and the inner core 202. The rupture disks 250 may be formed from a polymer, such as plastic, or other suitable material having a known pressure rating. As will be appreciated, the rupture disks 250 may rupture when a pressure differential across the first plug 52 is greater than the pressure rating of the rupture disks 250. The rupture disks 250 may be designed or selected (e.g., material, thickness, size, etc.) to shatter at any desired pressure. Once the rupture disks 250 shatter, the rupture disk ports 252 may be opened to enable fluid (e.g., cement) to flow through the first plug 52. As described in detail below, the rupture disks 250 may be configured to shatter upon application of sufficient pressure from cement pumped into the casing string 28 when the first plug 52 is at the bottom of the casing string 28 after being launched. With the rupture disks 250 shattered, cement can flow through the first plug 52 at the casing string 28 and into the annulus between the casing string 28 and the wellbore 30.

As will be appreciated, the components of the multi-plug launching system 50 may be sized or dimensioned based on the size (e.g., diameter) of the casing string 28. In certain embodiments, the diameter of the first plug 52 may be too small (e.g., due to a smaller diameter casing string 28) to accommodate the axial rupture disks 250 shown in FIG. 7. Accordingly, an alternative embodiment, which is shown in FIG. 9, may include radial rupture disks 260. The radial rupture disks 260 are secured to the central insert 204, and each radial rupture disk 260 occludes a respective radial rupture disk port 262, which extends from an outer radial surface 264 of the central insert 204 to the central passage 214 of the central insert 204. As shown in FIG. 9, the smallest diameter 222 of the tapered throat portion 216 of the central insert 204 is disposed axially above the radial rupture disk ports 262. Thus, when a solid ball 266 occludes the central passage 214 (e.g., when the first plug 52 is launched down the casing string 28), the solid ball 266 will not occlude the radial rupture disk ports 262. In this way, the first plug 52 may first be launched down the casing string 28 (e.g., with the solid ball 266 occluding the central passage 214), and the radial rupture disks 260 may be shattered to enable cement flow through the radial rupture disk ports 262 after the first plug 52 has been launched to the bottom of the casing string 28.

FIGS. 10-15 are various cross-sectional side views of the multi-plug launching system 50 and its components disposed within the casing string 28, illustrating the operation of the multi-plug launching system 50. First, FIG. 10 is a partially cross-sectional side view of the multi-plug launching system 50 after the multi-plug launching system 50 is stabbed into the casing string 28 with the gripping device 44 (e.g., casing running tool or casing drive system). As described in detail above, the first plug 52 is disposed at the bottom of the multi-plug launching system 50 and is coupled to the second plug 54 via shear screws 90. The second plug 54 is coupled to the plug system adapter 56 via shear screws 76. The central passage 118 of the second plug 54 and the central passage 214 of the first plug 52 are both unobstructed.

When the multi-plug launching system 50 is initially inserted or “stabbed” into the casing string 28, the internal cavity 82 of the casing string 28 below the multi-plug launching system 50 may be filled with drilling mud, as indicated by arrow 300. To clean or wipe the internal surface 80 of the casing string 28, the first plug 52 may be launched down the casing string 28. In certain embodiments, an amount of spacer fluid may be pumped into the casing string 28 before the first plug 52 is launched. To launch the first plug 52 down the casing string 28, a first solid ball 310 (e.g., small solid ball) is launched down the multi-plug launching system 50. As shown in FIG. 11, the first solid ball 310 passes through the plug system adapter 56 and the central passage 118 of the second plug 54 to reach the first plug 52. The first solid ball 310 is sized such that it will become lodged or landed against the smallest diameter 222 of the tapered throat portion 216 of the first plug 52. As discussed above, the first solid ball 310 has a diameter that is smaller than the smallest diameter 126 of the central passage 118 of the second plug 54 to enable passage of the first solid ball 310 through the second plug 54 without disturbing the second plug 54. For example, the first solid ball 310 may have a diameter of approximately 1 3/16″.

With the first solid ball 310 lodged in the smallest diameter 222 of the first plug 52, a first fluid may be pumped through the multi-plug launching system 50 (e.g., through the plug system adapter 56 and the central passage 118 of the second plug 54 to reach the occluded central passage 214 of the first plug 52, as indicated by arrow 312. For example, the first fluid may be a spacer fluid or a cement slurry. As pressure builds behind the first solid ball 310 in the first plug 52, the pressure will overcome the shear strength of the shear screws 90 coupling the first plug 52 to the second plug 54.

FIG. 12 is a partially cross-sectional side view of the multi-plug launching system 50 after the shear screws 90 have sheared and the first plug 52 has initially launched down the casing string 28. After the first plug 52 initially launches down the casing string 28, a cement slurry may be pumped into a space 320 in the casing string 28 between the first plug 52 and the second plug 54 to drive the first plug 52 down to the bottom of the casing string 28, as indicated by arrow 322. That is, the cement slurry may be pumped through the gripping device 44, through the plug system adapter 56, through the second plug 54, and into the space 320 within the casing string 28. The cement slurry may be pumped into the space 320 between the first plug 52 and the second plug 54 until the first plug 52 reaches the bottom of the casing string 28.

For example, FIG. 13 is a cross-sectional side view of an axial bottom 330 of the casing string 28, illustrating a float shoe 332 coupled to the axial bottom 330 of the casing string 28 with the first plug 52 landed against the float shoe 332. While the first plug 52 is landed against the float shoe 332 at the axial bottom 330 of the casing string 28, in other embodiments the first plug 52 may be landed against another stopping mechanism at the axial bottom 330 of the casing string 28. Although the first plug 52 is landed against the float shoe 332, the cement slurry may continue to be pumped into the casing string 28 to build pressure behind the first plug 52 at the axial bottom 330 of the casing string 28. Specifically, the cement slurry may be pumped into the casing string 28 until the rupture disks 250 shatter to open the rupture disk ports 252 in the first plug 52. Shattering of the rupture disks 250 may be verified using a variety of methods. For example, the cement slurry may be pumped into the casing string 28 behind the first plug 52 until a desired volume of cement slurry has been pumped into the casing string 28. For example, the desired volume of cement slurry may be based on a known size (e.g., length and diameter) of the casing string 28 and a known strength of the rupture disks 250. Alternatively, the cement slurry may be pumped into the casing string 28 until a desired and measured pressure of cement slurry within the casing string 28 is reached. Similarly, the desired pressure of cement slurry within the casing string 28 may be based on a known size of the casing string 28 and a known strength of the rupture disks 250. It should be noted that the first solid ball 310 (e.g., small solid ball) remains lodged in the tapered throat portion 216 during this process and does not allow cement slurry to flow through the central passage 214 of the first plug 52.

As discussed above, once the rupture disks 250 shatter, the rupture disk ports 252 may be opened, and the cement slurry within the casing string 28 may flow into the annulus between the casing string 28 and the wellbore 30. In the illustrated embodiment, the cement slurry flows through the rupture disk ports 252, as indicated by arrows 334, and through the float shoe 332. The cement slurry may flow through a valve 336 (e.g., a one-way valve, check valve, etc.) of the float shoe 332 and out of the float shoe 332 into the annulus, as indicated by arrows 338. Thereafter, cement slurry may continue to be pumped through the casing string 28 and into the annulus until a desired amount of cement slurry has been pumped.

After the desired amount of cement slurry has been pumped, a second solid ball 350 may be launched into the multi-plug launching system 50, as shown in FIG. 14. For example, the second solid ball 350 (e.g., large solid ball) may travel through the gripping device 44, the plug system adapter 56, and into the tapered throat portion 120 of the second plug 54. The second solid ball 350 is sized such that it will become lodged or landed against the smallest diameter 126 of the tapered throat portion 120 of the second plug 54. For example, the second solid ball 350 may have a diameter of approximately 1½″.

With the second solid ball 350 lodged in the smallest diameter 126 of the second plug 54, a second fluid may be pumped through the multi-plug launching system 50 (e.g., through the plug system adapter 56 to reach the occluded central passage 118 of the second plug 54, as indicated by arrow 352. For example, the second fluid may be a displacement fluid. As pressure builds behind the second solid ball 350 in the second plug 54, the pressure will overcome the shear strength of the shear screws 76 coupling the second plug 54 to the plug system adapter 56.

FIG. 15 is a cross-sectional side view of the multi-plug launching system 50 after the shear screws 76 have sheared and the second plug 54 has initially launched down the casing string 28. After the second plug 54 initially launches down the casing string 28, the displacement fluid may continue to be pumped into a space 360 in the casing string 28 between the second plug 54 and plug system adapter 56 to drive the second plug 54 down to the bottom of the casing string 28 (e.g., to land against the first plug 52), as indicated by arrow 362. That is, the displacement fluid may be pumped through the gripping device 44, through the plug system adapter 56, and into the space 360 within the casing string 28. The displacement fluid may be pumped into the space 360 between the plug system adapter 56 and the second plug 54 until the second plug 54 reaches the bottom of the casing string 28. After the displacement fluid is pumped into the casing string 28, the displacement fluid may be locked in until the cement slurry previously pumped into the casing string 28 is cured.

As discussed in detail above, present embodiments provide a system and method for launching multiple cement plugs (e.g., first and second plugs 52 and 54) within the casing string 28 or other tubular string. For example, during casing cementing operations. Specifically, present embodiments include the multi-plug launching system 50 having the first plug 52 (e.g., a bottom plug) and the second plug 54 (e.g., a top plug), which are coupled to one another via the shear screws 90. The second plug 54 (e.g., the top plug) is also coupled to the plug system adapter 56 via shear screws 76 to enable coupling of the first plug 54 and the second plug 56 to the gripping device 44 (e.g., a casing running tool or casing drive system). With the first and second plugs 52 and 54 coupled to the gripping device 44, the multi-plug launching system 50 may be inserted into (e.g., “stabbed” into) the casing string 28. The first and second plugs 52 and 54 each include a port (e.g., central passages 214 and 118, respectively) to allow a fluid (e.g., spacer fluid, cement, etc.) to pass through the plugs 52 and 54 and into the casing sting 28.

After a casing running operation is completed, the casing string 28 within the wellbore 30 may be filled with drilling mud. Prior to beginning a casing cementing process, the first solid ball 310 (e.g., small solid ball) is launched to occlude the central passage 214 of the first plug 52. Thereafter, a cement slurry and/or a spacer fluid is pumped through the second plug 54 (e.g., top plug) and behind the first solid ball 310 and first plug 52, thereby creating pressure and causing shear screws 90 coupling the first plug 52 to the second plug 54 to shear to launch the first plug 52. After the first plug 52 is launched, cement is pumped through the second plug 54 and behind the first plug 52 to drive the first plug 52 down the casing string 28 until the first plug 52 reaches the axial bottom 330 of the casing string 28. As discussed above, the first plug 52 also includes rupture disks 250 that occlude rupture disk ports 252 of the first plug 52. The cement may be pumped through the second plug 54 and into the casing string 28 until the rupture disks 250 of the first plug 52 at the axial bottom 330 of the casing string 28 shatter and open the rupture disk ports 252. With the rupture disk ports 252 of the first plug 52 opened, the cement may flow out of the casing string 28 and into an annulus between the casing string 28 and the wellbore 30.

Once a desired or calculated amount of the cement is pumped through the second plug 54 into the casing string 28 (e.g., to rupture the rupture disks 250 of the first plug 52 at the axial bottom 330 of the casing string 28 and/or fill the annulus between the casing string 28 and the wellbore 30), the second solid ball 350 is launched to occlude the central passage 118 of the second plug 54. Thereafter, a displacement fluid (e.g., water or a water mixture) is pumped behind the second solid ball 350 (e.g., large solid ball) and the second plug 54, thereby creating pressure and causing shear screws 76 coupling the second plug 54 to the plug system adapter 56 to shear and launch the second plug 54 down the casing string 28. Thereafter, the displacement fluid may be locked in the casing string 28 until the previously-pumped cement is cured. As discussed above, present embodiments of the multi-plug launching system 50 are shorter and more compact than traditional multi-plug launching systems. Thus, as the disclosed systems are inserted into the casing string 28, they may take up little or no stack-up room on the derrick or rig 10.

While the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and tables and have been described in detail herein. However, it should be understood that the embodiments are not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. Further, although individual embodiments are discussed herein, the disclosure is intended to cover all combinations of these embodiments. 

1. A multiple cement plug launching system, comprising: a plug system adapter assembly; a first plug assembly comprising a first central passage; a second plug assembly comprising a second central passage; a first plurality of shear screws coupling the first plug assembly to the second plug assembly; and a second plurality of shear screws coupling the second plug assembly to the plug system adapter.
 2. The multiple cement plug launching system of claim 1, wherein a first total number of the first plurality of shear screws is less than a second total number of the second plurality of shear screws.
 3. The multiple cement plug launching system of claim 1, wherein a first shear strength of the first plurality of shear screws is less than a second shear strength of the second plurality of shear screws.
 4. The multiple cement plug launching system of claim 1, wherein the first plug assembly comprises a plurality of rupture disks, wherein each rupture disk of the plurality of rupture disks occludes a respective one of a plurality of rupture disk ports extending through the first plug assembly.
 5. The multiple cement plug launching system of claim 4, wherein the plurality of rupture disk ports extend axially through an outer body and an inner core of the first plug assembly.
 6. The multiple cement plug launching system of claim 4, wherein the plurality of rupture disk ports extend radially through a central insert of the first plug assembly.
 7. The multiple cement plug launching system of claim 1, wherein the plug adapter assembly, the first plug assembly, and the second plug assembly are coupled to one another in an axial arrangement, the first plug assembly is disposed at an axial bottom of the multiple cement plug launching system, and the plug adapter assembly is disposed at an axial top of the multiple cement plug launching system.
 8. The multiple cement plug launching system of claim 1, wherein the plug adapter assembly comprises a threaded portion at an axial top of the plug adapter assembly, wherein the threaded portion is configured to threadingly engage with a gripping device of a drilling rig.
 9. The multiple cement plug launching system of claim 1, wherein the first central passage comprises a first tapered throat portion comprising a first smallest diameter, the second central passage comprises a second tapered throat portion comprising a second smallest diameter, and wherein the first smallest diameter is smaller than the second smallest diameter.
 10. A method, comprising: inserting a multiple cement plug launching system within a casing string, wherein the multiple cement plug launching system comprises a first plug assembly, a second plug assembly coupled to the first plug assembly, and a plug system adapter assembly coupled to the second plug assembly; launching the first plug assembly down the casing string; rupturing a plurality of rupture disks of the first plug assembly after launching the first plug assembly down the casing string; and launching the second plug assembly down the casing string after rupturing the plurality of rupture disks in the first plug assembly.
 11. The method of claim 10, wherein launching the first plug assembly down the casing string comprises shearing a plurality of shear screws coupling the first plug assembly to the to the second plug assembly.
 12. The method of claim 11, comprising occluding a first central passage of the first plug assembly with a first solid ball and building pressure behind the first solid ball and the first plug assembly with a fluid to shear the plurality of shear screws, wherein the fluid comprises a spacer fluid, a cement slurry, or a combination thereof, and wherein the first solid ball comprises a ball diameter larger than a first diameter of the first central passage and smaller than a second diameter of a second central passage of the second plug assembly.
 13. The method of claim 10, wherein launching the second plug assembly down the casing string comprises shearing a plurality of shear screws coupling the second plug assembly to the plug system adapter assembly.
 14. The method of claim 13, comprising occluding a central passage of the second plug assembly with a solid ball and building pressure behind the solid ball and the second plug assembly with a fluid to shear the plurality of shear screws, wherein the fluid comprises a displacement fluid.
 15. The method of claim 10, comprising pumping a cement slurry down the casing string, through the first plug assembly, and into an annulus between the casing string and a wellbore after rupturing the plurality of rupture disks of the first plug assembly and before launching the second plug assembly down the casing string.
 16. The method of claim 10, comprising coupling multiple cement plug launching system to a tubular gripping system of a drilling rig and inserting the multiple cement plug launching system into the casing string with the tubular gripping system.
 17. A system, comprising: a multiple cement plug launching system, comprising: a plug system adapter assembly; a first plug assembly comprising a first central passage and a plurality of rupture disks, wherein each rupture disk of the plurality of rupture disks occludes a respective one of a plurality of rupture disk ports extending through the first plug assembly; and a second plug assembly comprising a second central passage, wherein the plug system adapter assembly is coupled to the second plug assembly, which is coupled to the first plug assembly, such that the plug system adapter assembly, the second plug assembly, and the first plug assembly are coupled to one another in an axial arrangement.
 18. The system of claim 17, wherein the first plug assembly is coupled to the second plug assembly with a first plurality of shear screws, the second plug assembly is coupled to the plug system adapter assembly with a second plurality of shear screws, and a first total number of the first plurality of shear screws is less than a second total number of the second plurality of shear screws.
 19. The system of claim 17, comprising a tubular gripping device of a drilling rig, wherein the plug system adapter is coupled to the tubular gripping device via a threaded connection.
 20. The system of claim 17, wherein the first central passage comprises a first tapered throat portion comprising a first smallest diameter, the second central passage comprises a second tapered throat portion comprising a second smallest diameter, and wherein the first smallest diameter is smaller than the second smallest diameter. 